There are many reasons for the failure of dog vaccination, as follows: 1. The dog is in poor physical condition when vaccinated, with symptoms of vomiting and diarrhea, so the vaccine has no effect when it reaches the body. 2. Injecting the dog If the vaccine is placed in the wrong place, the vaccinated vaccine will lose its efficacy during storage, so it will have no effect in the dog's body. 3. There are other viruses in the dog's body during the vaccination, which will resist the vaccine in the body, causing the vaccine to be ineffective.